Fastener driving tool



Jan. 20, 1970 K. DIEHL FASTENER DRIVING TOOL Filed Nov. 8. 1966 2Sheets-Sheet l www m w MNA www

U.S. Cl. 227- 11 Claims ABSTRACT 0F THE DISCLOSURE An explosion-actuatedfastener driving tool in which detent means cooperate with the drivingpiston of the tool to yieldably hold the piston in a retracted positionand in which the detent means comprise retainer means radially movablesupported in the barrel in which the piston is slidably guided andbiasing means in form of a split ring for urging the retainer meansagainst the piston.

The present invention relates to improvements in explosion-actuatedtools or pistols for driving studs, bolts, nails or analogous fastenersinto masonry walls, wooden boards and similar workpieces.

Presently known fastener driving tools normally cornprise a barrel whichaccommodates a reciprocable piston and has an open forward end adaptedto receive a fastener. The piston is movable to and from a retractedposition and leaves such retracted position in response to firing of anexplosive cartridge. Detent means must be provided to yieldably hold thepiston in retracted position, and it was found that conventional detentmeans are not entirely satisfactory. This is due to the fact that thespace in a compact, lightweight fastener driving tool 1s limited andthat the provision of detent means should not unduly weaken the pistonand/or the barrel and should not contribute excessively to the bulk,weight and initial cost of the implement. If the detent means is to actupon the stem of the piston, it must extend considerably into the highlystressed front portion of the barrel. On the other hand, and if thedetent means is provided on the so-called boss at the trailing end ofthe piston, its parts are exposed to hot products of combustion in therange of several hundred degrees C. and to pressures often exceeding1,000 atmospheres. This excludes the utilization of parts which consistof rubber and also all readily availableand relatively cheap syntheticplastic substances. Furthermore, and if the detent means is installed inor on the stem of the piston, the latter is weakened and might not beable to withstand the aforementioned temperatures or pressures.Overdimensioning of the piston is not possible without undue increase inweight, maneuverabilily, bulk and cost of the tool.

As a rule, conventional fastener driving tools comprise detent meanswhich are installed on the piston proper and act outwardly, i.e., in adirection toward the barrel of the tool. If is known to utilize ringswhich are recessed into the piston and slide along the internal surfaceof the barrel. Such rings weaken the piston, i.e., that element of thetool which is subjected to highest stresses, so that the life expectancyof the piston is very short Accordingly, it is an important Object ofthe present invention to provide a fastener driving tool or piston withnovel and improved detent means for holding the piston in retractedposition prior to firing of an explosive charge and to construct andassemble the detent means in such a way that its provision does notweaken or otherwise unfavorably affect the piston.

Another object of the invention is to provide novel detent means whichcan be readily incorporated in pres- 3,490,673 Patented Jan. 20, 1970ently known fastener driving tools without necessitating extensivealterations in the design of such tools.

A further object of the instant invention is to provide very simple,long-lasting, compact and inexpensive detent means and to mount thedetent means outside of the high-pressure and high-temperature zones ina fastener driving tool.

A concomitant object of the invention is to provide detent means whosecomponents may be readily reached, inspected or replaced in response tomere partial dismantling of the fastener driving tool.

Briefly stated, one feature of my invention resides in the provision ofa fastener driving tool which comprises a housing having a front endarranged to accommodate a stud, pin, nail or an analogous fastener and arear end adjacent to a cartridge chamber or firing chamber, an elongatedbarrel received in the housing, a piston reciprocably received in thebarrel and movable to and from a retracted position spaced from thefastener in the front end of the housing, and detent means for yieldablyholding the piston in retracted position, The detent means comprisesretainer means radially movably supported by the barrel and biasingmeans for urging the retainer means against the piston. Such retainermeans may comprise one or more preferably spherical members reciprocablein radial aperture or apertures of the barrel and an annular member ofspringy material arranged to urge the retainer or retainers intofrictional engagement with the peripheral surface of the piston. Theannular member may be constituted by a split ring of spring steel or thelike, and the retainer means may extend into the slot of such split ringto widen the slot in response to radially outward movement under theaction of the piston when the latter leaves its retracted position. Theperipheral surface of a portion of the piston may be congurated in sucha way that the piston automatically shifts the retainer means radiallyoutwardly whereby the thus deformed annular member bears against theadjoining portion of the housing and is propped or Supported againstexcessive radial expansion.

The novel features which are considered as characteristic of theinvention are set forth in particular in the appended claims. Theimproved fastener driving tool itself, however, both as to itsconstruction and its mode of operation, together with additionalfeatures and advantages thereof, will be best understood upon perusal ofthe following detailed description of certain specific embodiments withreference to the accompanying drawings, in which:

FIG. 1 is an axial section through a fastener driving tool which isprovided with a detent means embodying one rform of the presentinvention, the tool being shown in idle position;

FIG. -2 is a similar axial section through the barrel of the fastenerdriving tool which is shown in cocked position ready to drive a fastenerpin into a hard workp1ece;

FIG. 3 shows the structure of FIG. 2 ready to drive a fastener pin intoa relatively soft workpiece;

FIG. 4 is an enlarged fragmentary axial section through the housing of asecond fastener driving tool which is provided with modified detentmeans; and

FIG. 5 is a transverse section as seen in the direction of arrows fromthe line V*V of FIG. 4.

Referring to the drawings in detail, and first to FIGS. 1 to 3, there isshown a fastener driving tool or pistol which comprises a compositehousing including a tubular front portion 10 and a tubular rear portion11. The front portion 10 is reciprocable, within limits, with referenceto the rear portion 11 and its rear end is -telescoped into the frontend of the rear portion. The volume of an annular compartment 12 in thefront end of the rear portion 11 will increase or decrease, depending onthe axial position of the front portion 10. This compartment 12 isconstituted by a counterbore drilled into the front end of the rearportion 11. The means for guiding the front portion 1() during its axialmovement comprises a split ring 15 extending into a circumferentialgroove 13 of the front portion 10 and into an elongated annular groove14 machined into the internal surface of the rear portion 11. The axiallength of the groove 14 exceeds the axial length of the split ring 15 sothat the front portion can be shifted by a distance corresponding to theaxial length of the unfilled portion of the groove 14. The ringsimultaneously serves as a means for coupling the portions 10, 11 toeach other. The axial length of the circumferential groove 13 equals orapproximates that of the ring 15. It is clear that the groove 13 will belonger if the groove 14 receives the ring 15 without any or with minimalfreedom of axial movement.

In order to permit separation of tubular portions 10 and 11, the depthof the groove 13 is suicient to accornmodate the entire split ring 15.To this end, the rear portion 11 is provided with one or more openings(not shown) which communicate with the groove 14 and enable the operatorto force the ring 15 into the groove 13 by resorting to a rudimentarytool, whereupon the rear end of the front portion 10 is readilywithdrawable from the compartment 12.

The firing mechanism is denoted by the numeral 26. The details of thisfiring mechanism are known from the art of conventional fastener drivingtools and need not be described here. It is to be noted that other typesof firing mechanisms can be employed in the tool of FIGS. 1 to 3 withoutdeparting from the spirit of the present invention. The front end of thecasing 26a of the flring mechanism 26 is adjacent to the rear end of thetubular portion 11, and more particularly to a ring 16 which is affixedto and extends rearwardly from the tubular portion 11. In theillustrated embodiment, the ring 16 constitutes a further or rearmosttubular portion of the housing and is detachably coupled to the rearportion 11 by threads 17. Such detachability of the ring 16 is desirablein order to afford access to component parts which are installed in theinterior of the barrel. In fully assembled position, the front end faceof the ring 16 bears against an external annular shoulder of the rearportion 11.

The housing 10, 11, 16 accommodates a piston 18 which is reciprocable inan elongated cylindrical barrel 19, a composite resilient element 20, acylindrical piston guide 36, and detent means 28 for the piston 18. Themajor part of the sleeve 19 is accommodated in the rear portion 11 andhas a cylindrical bore 21 for the piston 18. The front end portion ofthe barrel 19 has radially extending ports 22 and its rear end portionextends into and rearwardly beyond the ring 16. The rear end of the bore21 communicates with a forwardly flaring conical passage 23 located infront of a short cylindrical throat 24, the latter being provided infront of a cylindrical cartridge chamber or firing chamber 25. Thethroat 24 constitutes a combustion chamber.

The rear end portion of the barrel 19 which defines the passage 23,throat 24 and cartridge chamber 25 is provided with an external ange 27which is tted into the ring 16. The flange 27 constitutes one element ofmeans for limiting axial movements of the sleeve 19 and its end facesrespectively cooperate With internal shoulder of the ring 16 todetermine the rear end position and with the rear end face of the rearportion 11 to determine the front end position of the barrel. FIG. 1shows the barrel 19 in its front end position in which the flange 27abuts against the rear end face of the tubular portion 11. In FIGS. 2and 3, the barrel 19 is shown in its rear end position in which the ange27 abuts against the internal shoulder of the ring 16. Rearwardly of theange 27, the external diameter of the barrel 19 de- 4 creases and suchdecrease is in part stepwise and in part gradual. Portions of the barrel19 are slidably guided in the rear portion 11 and ring 16. The rearportion 11 is provided ywith one or more internal recesses 38 whichsurround an intermediate portion of the barrel 19.

The piston 18 comprises an elongated forward portion or stem 33 and alarger-diameter rearward portion or boss 29 which is adjacent to thepassage 23. This boss 29 is slidably guided in the bore 21 of the sleeve19. The stem 33 is slidably guided in parts lwhich are installed in thefront portion 10. The detent ymeans 28 is installed in the sleeve 19forwardly of the flange 27 and cooperates with the boss 29. The exactconstruction of detent means 28 will be described hereinafter.

The aforementioned resilient element 20 is installed in the rear regionof the front portion 10. This resilient element 20 comprises asubstantially cup-shaped member 39 whose bottom `wall is provided at itsrear end, namely, at that end which is nearer to the firing mechanism26. The bottom wall has an opening 40 whose diameter exceeds slightlythe diameter of the boss 29 so that the latter can enter the bottom wallwhen the piston 18 is caused to perform a working stroke. In the regionwhere the bottom wall meets the annular side wall of the cupshapedmember 39, the latter comprises apertures or ducts 41 which communicatewith the compartment 12.

The cup-shaped member 39 accommodates a short cylinder 42 ofsubstantially U-shaped cross-sectional outline. The bottom wall of thecylinder 42 is adjacent to the bottom wall of the mem-ber 39 and has anopening 45 which receives, without clearance, the stem 33 of the piston18. Thus, the bottom wall of the cylinder 42 serves as a means forguiding the stem 33 -when the piston reciprocates in the barrel 19. Theexternal surface of the cylinder 42 tapers rearwardly toward the iiringmechanism 26 so that the cylinder 42 and the cup-shaped member 39 definebetween themselves an annular gap 54 of wedge-like cross-sectionaloutline. This enables the cylinder 42 to expand radially in response tothe engagement of its bottom wall by the boss 29 of the piston 18. Asclearly shown in FIG. 1, the rear surface of the bottom wall of thecylinder 42 is inclined forwardly toward the axis of the housing asindicated at 46.

The cylinder 42 is installed immediately behind an annular shockabsorber or cushion 43 which consists of rubber or other highly elasticmaterial. The cushion 43 is separated from the stem 33 by a cylindricalliner 44 whose rear end vface is normally separated from the bottom wallof the cylinder 42 by an annular clearance 52. This cushion 43 isinstalled in the annular wall of the cup-shaped member 39 but isnormally separated therefrom by a narrow annular clearance 53. 'Thelatter will disappear in response to axial compression and resultingradial expansion of the cushion 43 when the boss 29 of the piston 18strikes against the inclined rear end face 46 of the cylinder 42. Thecushion 43 abuts against the front end face of the cylinder 42 andagainst the rear end face of the cylindrical guide 36 for the stem 33,the guide 36 having a bore 50 which can receive the stern 33 and iscoaxial with the bore of the liner 44. The front end face of the cushion-43 also abuts against a circumferential shoulder of the liner 44. Suchshoulder is formed at the point where the smaller-diameter rear portionof the liner 44 meets its larger-diameter front portion. The frontportion of the liner 44 is received in a counterbore 47 of the guide 36.A washer 48 of rubber or other suitable elastomeric material isinstalled between an external shoulder of the guide 36 and an internalshoulder of the front portion 10.

As stated before, FIG. 1 shows the fastener driving tool in idleposition in which the ange 27 of the barrel 19 abuts against the rearend face of the rear portion 11. FIG. 2 illustrates the tool in cockedposition with a short fastener pin 49 inserted into the front end of thefront portion 10. The shaft of the fastener pin 49 carries a collar 51which abuts against the front end face of the guide 36. Thelarger-diameter rear portion of the pin 49 is received with little or noclearance in the front part of the bore 50. The front end face of thefront portion has a concentric undercut recess 56 which receives a ring55 consisting of highly heat-resistant elastomeric material. The tip ofthe pin 49 abuts against a relatively hard workpiece W, e.g., a masonrywall made of concrete or the like. This workpiece does not yield tomanually applied pressure so that, when the operator exerts pressureagainst the housing 10, 11, 16, the guide 36 yields and moves rearwardlyby pushing the cupshaped member 39 and cushion 43 toward the liringmechanism. In FIG. 3, the front end face of the front portion 10 ispressed against a relatively soft workpiece W', e.g., a board made ofsoft wood, whereby the tip of the fastener pin 49 penetrates into theworkpiece W I and the rearward axial displacement of the guide 36 isshorter than in FIG. 2. In other words, the exact axial position of thefastener pin 49 prior to tiring of a cartridge in the chamber 25 dependson the hardness of the workpiece into which the pin is to be driven inresponse to actuation of the firing mechanism 26. Irrespective of thestarting position of the fastener pin 49, the tool of FIG. 2 or 3 isready for firing when the barrel 19 is shifted rearwardly through apredetermined minimal distance and the piston 18 assumes its retractedposition in which the stem 33 is spaced from the fastener pin 49.

The detent means 28 of FIGS. l to 3 is constructed and installed for thepurpose of yieldably holding or retaining the piston 18 in the retractedposition shown in FIG. 2 or 3, namely, in a position in which the frontend of the stem 33 is spaced from the fastener pin 49. This detent meanscomprises a spherical retainer 31 and an elastically deformable annularbiasing member here shown as a split elastic ring 30. The retainer 31 isreciprocable in a radial aperture 32 of the barrel 19 and this apertureis dimensioned in such a way that a portion of the retainer can extendinto the bore 21 to engage the peripheral surface of the boss 29.Another portion of the retainer 31 extends radially outwardly beyond theaperture 32 and is biased by the ring 30 which latter tends to urge theretainer against the peripheral surface of the boss. Such bias sufficesto yieldably hold the piston 18 in retracted position so that the stem33 is spaced from the fastener pin 49.

The rear porton 11 is provided with an internal annular groove 37 (seeFIG. 2 or 3) which receives `the ring 30 when the barrel 19 is held inits front end position shown in FIG. 1. The rear portion of the barrelformed with a peripheral groove 35 which can receive at least a portionof the ring 30 so that the latter is thereby held against axialdisplacement with reference to the barrel.

It will be seen that the provision of the detent means 28 does not inany way weaken the piston 18 and that the major part of this detentmeans is loca-ted outside of the path of hot combustion products and isnot subjected to excessive pressures. The holding action of thespherical retainer 31 is very reliable but this retainer willimmediately release vthe boss 29 when a cartridge in the chamber 25 isfired in response to actuation of the firing mechanism 26. The piston 18is then propelled forwardly and its stem 33 drives the fastener pin 49linto the workpiece W or W.

The manner in which the piston 18 can be moved back to retractedposition and in which a cartridge can be introduced into the chamber 25is known from the art and need not be described here.

Referring now to FIGS. 4 and 5, there is shown a moditied detent means28' which may be used as a substitute for the detent means 28 of FIGS. lto 3. This detent means 28 again comprises a spherical retainer 31 and amodified elastic biasing ring 30. The ring 30 is slotted (i.e., it isconstituted by a split ring), the slot being shown at 34 and receiving aportion of the retainer 31. The barrel 19 has a peripheral groove 35which receives a portion of the ring 30' so that the latter is compelledto share all axial movements of the barrel. The piston 18 of the toolshown in FIGS. 4 and 5 has a frustoconical rearward portion or boss 29'which tapers forwardly toward the stem 33. This leaves an annular gap 57of wedge-like cross-sectional outline whose width increases forwardly(see FIG. 4). The bias of the ring 30' is sufficient to urge the innerportion of the retainer 31 against the conical peripheral surface of theboss 29 whereby the piston 18 is held in retracted position. When acartridge which has been inserted into the chamber 25 is red in responseto actuation of the tiring mechanism (not shown in FIGS. 4 and 5), thepressure of gases in the throat 24 overcomes the bias of the ring 30whereby the conical boss 29 pushes the retainer 31 radially outwardlyand the piston 18 is propelled into engagement with the fastener. Thebias of the ring 30 need not be strong, as long as it suices to retainthe piston 18' in retracted position. The force exerted by combustionproducts upon the rear end face of the boss 29 exceeds many times thebias of the ring 30. Such combustion products will cause the retainer 31to expand the ring 30 whereby at least a portion of the external surfaceof the ring comes in actual abutment with and is supported or proppedlby the internal surface of the ring 16. The same holds true for therings 16, 30 of the embodiment shown in FIGS. 1 to 3. The componentparts of the detent means 28 or 28 preferably consist of metallicmaterial.

An important advantage of the detent means 28 or 28 is seen to reside inthat the retainer 31 and/or the ring 30 or 30 need not be mounted on thepiston 18 or 18'. The retainer 31 merely bears against the strongestportion of the piston, namely, against the boss 29 or 29' so that theprovision of such detent means does not shorten the useful life of thepiston. As stated before, the retaining action of the biasing means 28or 28 need not be very strong, as long as the piston 18 or 18 is safelyheld in retracted position prior to liring of a cartridge. The detentmeans remains effective for long periods of use because the ring 30 or30 is not directly exposed to elevated temperatures and/or pressures sothat its elasticity remains intact. In addition, the inertia of thedetent means is negligible so that the retainer responds immediately,either to engage and hold the piston or to` release the piston inresponse to buildup of pressure in the throat 24. No plastic deformationof the detent means takes place during tiring and its operation is notaffected by combustion products.

Due to the fact that the external surface of the elastic ring 30 or 30can be moved into actual engagement with the internal surface of theadjoining portion of the barrel, the ring is subjected to negligibletangential stresses despite the fact that its expansion is practicallyinstantaneous. The clearance between the external surface of the ring 30or 30 and the adjoining portion of the housing is preferably small sothat such external surface is propped in response to relatively smallradial expansion of the ring.

That portion of the ring 30 or 30 which is subjected to strongestbending stresses is located diametrically opposite the retainer 31. Thisis of advantage because the propagation of Ibending stresses from theregion of corttact with the retainer 31 to the portion which undergoesmaximal bending stresses must take place along one-half of thecircumferential length of the ring 30 or 30 whereby the latter absorbs asubstantial part of such stresses and remains intact for long periods ofactual use.

Of course, the improved fastener driving tool is susceptible of manyadditional modifications without departing from the spirit of thepresent invention. For example, the detent means 28 or 28 may bereplaced by other types of analogous detent means, or such detent meansmay be multiplied. Also, the spherical retainer 31 may be replaced by apinor stud-shaped retainer lwith a preferably spherical or semisphericalhead which is reciprocable radially of the barrel 19 so that its headcan bear against the piston. Moreover, each of the detent means maycomprise a single elastic ring and two or more retainers 31. The ring 30or 30 may `be replaced by other types of resilient biasing means capableof urging the retainer or retainers 31 (or analogous retainers) intosatisfactory holding engagement with the piston 18 or 18.

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can, by applying current knowledge,readily adapt it for various applications without omitting featureswhich fairly constitute essential characteristics of the generic andspecific aspects of my contribution to the art and, therefore, suchadaptations should and are intended to be comprehended within themeaning and range of equivalence of the following claims:

What is claimed as new and desired to be protected by Letters Patent is:

1. An explosion-actuated fastener driving tool cornprising a housinghaving a front end arranged to accommodate a fastener and a rear endadjacent to a firing chamber; an elongated barrel received in saidhousing; a piston reciprocably received in said barrel and movable toand from a retracted position spaced from said front end of saidhousing; and detent means cooperating with said piston for yieldablyholding the latter in said retracted position, said detent meanscomprising retainer means radially movably supported by said barrel andbiasing means for urging said retainer means against said piston andcomprising a split ring having a slot into which a portion of saidretainer means extends, said piston cooperating with said retainer meansto move the latter rnomentarily in radially outward direction duringmovement of said piston away from said retracted position to thus movean increasing portion of said retainer means into said slot to therebyradially expand said split ring.

2. A fastener driving tool as defined in claim 1, wherein said retainermeans is reciprocable in a radial aperture of said barrel and comprisesportions extending inwardly and outwardly from said aperture, at leastthat portion of said retainer means which extends inwardly of saidbarrel being of spherical shape.

3. A fastener driving tool as defined in claim 1, wherein said pistonhas a conical peripheral surface which tapers forwardly and is engagedby said retainer means in the retracted position of said piston so thatsaid peripheral surface displaces the retainer means radially outwardlyin response to movement of said piston from retrated position on firingof a cartridge in said firing chamber.

4. A fastener driving tool as defined in claim 1, wherein said barrelhas a radially extending aperture accommodating said retainer means anda peripheral groove communicating with said aperture, at least a portionof said split ring being normally received in said peripheral groove.

5. A fastener driving tool as defined in claim 1, wherein said barrel isreciprocable, within predetermined limits, in the interior of saidhousing and wherein said housing comprises a series of coaxial tubularportions.`

6. A fastener driving tool as defined in claim 1, Wherein said pistoncomprises a smaller-diameter forward portion and a larger-diameterrearward portion, said detent means being arranged to engage with saidrearward portion `which latter is slidable in said barrel, and furthercomprising guide means provided in said housing for the forward portionof said piston.

7. A fastener driving tool as defined in claim 1, wherein said barrel isreciprocable in said housing and is shiftable rearwardly in response toaxial stresses transmitted thereto by a fastener which is introducedinto the front end of said housing.

8. A fastener driving tool as defined in 'claim 1, wherein said retainermeans comprises a ball of metallic material and said split ringconsisting of metallic material and being recessed into a peripheralgroove of said barrel.

9. A fastener driving tool as defined in claim 1, wherein said pistoncomprises a portion arranged to displace said retainer means radiallyoutwardly against the opposition of said biasing means in response tomovement of said piston from retracted position.

10. A fastener driving tool as defined in claim 1, wherein said pistonhas at a rear end portion thereof a surface portion engaging saidretainer means and constructed to momentarily move said retainer meansin radially outward direction during movement of said piston away fromsaid retracted position.

A11. A fastener driving tool as defined in claim 10, wherein saidretainer means is a ball reciprocable in a radial opening in saidbarrel, and wherein said housing has a rigid portion surrounding saidring with small clearance to limit radial expansion of said ring.

References Cited UNITED STATES PATENTS 1,726,012 8/1929 Bilz 227-1472,839,754 6/1958 Pfafrr 227-147 2,973,520 3/1961 Bell 227--147 3,055,0089/1962 Bell et al. 227-10 3,172,119 3/1965 Siddons 227-10 XR 3,255,9426/1966 Bell et al. 227-8 3,348,751 10/1967 Henning 227-8 GRANVILLE Y.CUSTER, IR., Primary Examiner

